This invention relates to a medical device capable of being used as both a dilator and a catheter. More particularly, this invention relates to a new and improved expandable dilator-catheter device having a structure analogous to a specially shaped inflatable balloon. It will be understood that while the present invention may be utilized in virtually any circumstance wherein a catheter or dilator is typically employed, it is particularly well-suited for urethral application. Accordingly, for the sake of clarity, the present invention and its developmental background will be principally discussed in terms of a urethra and bladder environment.
It is well recognized in the field of Urology that persons lose control of their urinary function. This loss of control may be temporary or permanent, depending upon the cause of the loss of urinary function. The bladder is a dome shaped container with muscular walls and which accepts urine from the kidneys for temporary storage. During normal voluntary urination, the muscles in the bladder wall contract and simultaneously the sphincter muscle surrounding the opening in the bladder which communicates with the urethra relaxes so that the urine stored in the bladder is released into the urethra and expelled from the body.
Since the loss of voluntary control over the urinary function is typically a secondary effect caused either by disease or trauma, it has become a well established medical practice to relieve the urinary drainage problem mechanically by means of the process of catheterization.
In the catheterization process, a tube or catheter is inserted into and through the urethra until the remote or distal end is located within the bladder, usually being disposed just past the sphincter muscle at the juncture of the bladder with the urethra. The near or proximal end of the tube remains outside of the body and there is thus provided a path or channel through which urine in the bladder can drain as the need arises. Once a catheter has been passed through the urethra and inserted into the bladder, it is generally necessary, in connection with the relevant disease and trauma conditions, to have the catheter retained in the urinary tract with the distal end of the catheter in the bladder, such retention being in the order of several days to several weeks without removal. Catheters which are designed for this use are called urinary retention catheters and are typically provided by including an inflatable balloon at the distal end of the catheter which is deflated during insertion of the catheter and which is inflated by passing a fluid, typically water or saline solution through a passage within the catheter, called an inflation lumen. Thereafter, fluid from the bladder drains through the main passage of the catheter, called the drainage lumen.
The basic design of commercially available prior art retention catheters has changed very little, and the well known Foley retention catheter is almost universally used by doctors, hospitals, nursing homes, etc. to alleviate loss of voluntary bladder control. Typical prior art catheters are usually formed of relatively thick walled construction so as to be insertable without buckling, have a rounded solid tip to prevent trauma to the delicate lining of the urethra, and have side openings adjacent the tip to communicate the interior of the bladder with the drainage lumen. The prior art catheters also have an inflatable balloon portion beyond the drainage opening in order to retain the catheter in place.
These catheters, and many more like them, are undesirable from the standpoint that considerable pain may be experienced in introducing a relatively wide, semi-rigid catheter into a relatively narrow urethra. Moreover, the inflatable balloon usually has a bulbous shape liquid-filled reservoir which is often uncomfortable and may lead to bladder spasms. Further, the small side openings can easily clog from clots of sediment material which collects in the bottom of the bladder. Still further, as a result of the solid tip, it is impossible to pass diagnostic or treatment instrumentation through the catheter for the purpose of inspecting or treating the interior of the bladder. The capability of inserting instrumentation through the catheter after it is in place is very important in the urological practice since prior treatment involves the use of anesthesia in order to insert steel tube instrumentation as has been the practice. Also, prior art catheters will often collapse when suction is applied, when, for example, blood clots are aspirated from the bladder.
Examples of prior art patents directed to catheters include, but are not limited to, U.S. Pat. Nos. 2,892,458, 2,936,761, 3,087,492, 3,292,627, and 3,394,705.
Similar to catheters, dilators are used extensively in the medical field for a variety of purposes. Generally, a dilator acts to progressively expand a narrow passageway in the body so that other instruments or the like may be passed therethrough. For example, in urology, and more specifically with urethral and ureteric lithiasis, the presence of calculus requires dilation in order to facilitate the intervention and the expulsion of the calculus formation. Currently, the treatment in such cases is to use a set of catheters, made of metal or other materials, which have gradually increasing diameters, so as to crush the calculus formation.
To produce the needed dilation, several methods are known in the medical art, including the laminae vegetales (still used, although infrequently), Champetier De Ribes's bladder, the Hegal dilators and various other dilators by now abandoned. The Hegal dilators are metal cones of progressively larger diameters, which are first introduced, left in situ for a while, and then extracted before applying cones of larger diameter.
The results obtained with these dilators are good, provided that they are handled by a skilled hand, thereby avoiding the risks of perforation and/or laceration as is the case whenever an object is introduced in tender parts of the human body. Unfortunately, the various dilating methods are not always entirely satisfactory, since they all exhibit limitations, potential hazards, and occasionally even applicational difficulties.
Clearly, it would be advantageous to combine the functions of a catheter and dilator in one medical instrument. A dilator-catheter of this type would preferably overcome the many deficiencies and problems related to known catheters and dilators as discussed above. Certain complicated attempts which have met limited success have been made toward this goal; for example, see U.S. Pat. Nos. 4,195,637, 4,271,839, 4,295,464, 4,318,410, and 4,338,942.
Accordingly, it is a principal object of the present invention to provide a dilation catheter device which overcomes the deficiencies of the prior art.
It is another object of the present invention to provide a medical device capable of performing both catheter and dilator functions, yet retaining a small diameter.
It is still another object of the present invention to provide a dilation catheter which will not collapse under an applied suction.
It is another object of the present invention to provide a dilation catheter having a more comfortable expandable retaining means.
It is yet another object of the present invention to provide a dilation catheter capable of expansion via both liquid and gaseous fluids.